The present invention pertains to medication delivery devices, and, in particular, to medication delivery devices that are reusable with replacement cartridges.
Patients suffering from a number of different diseases frequently must inject themselves with medications. A variety of devices have been proposed to facilitate these injections. One known type of device is a reusable injection pen. Such an injection pen is typically equipped with a cartridge including a plunger and containing a multi-dose quantity of liquid medication. A drive f the pen is movable forward by a dose delivery mechanism to advance the plunger in the cartridge in such a manner to dispense the contained medication through a needle that penetrates a septum at a forward end of the cartridge. After such a pen has been utilized to deliver multiple doses and exhaust the supply of medication within the cartridge, a user can remove and dispose of the spent cartridge. After a user installs a replacement cartridge, the reusable injection pen then can be used again to deliver its medication contents in a conventional manner.
At least one known reusable injection pen utilizes an electronics assembly to determine a set and injected dose by monitoring relative motions of components used in setting a dose, and components used in advancing a drive screw to inject the set dose, respectively. While useful, one shortcoming of this pen is that it provides no mechanism to track the amount of medication remaining in a cartridge. While medication delivery device designs are known that can track drive screw position sufficiently accurately throughout its operational travel path, which would allow drive screw travel remaining and thereby medication remaining to be determined, such designs may add complexity to the device.
Thus, it would be desirable to provide a reusable delivery device that can overcome one or more of these and other shortcomings of the prior art.